ABSTRACT:
Nanotechnology deals with the study of nano sized particles. With the study of nano size particles, devices and composites, we will find ways to make stronger materials, detect diseases in the bloodstream, build extremely tiny machines, generate light and energy and purify water. The most fascinating application of Nanotechnology is that we can transmit information at the speed of light more efficiently through Photonics communication using Photons. The main objective of this paper is to implement Nano technology in optical communication. Photonics communication speeds up telecommunications by replacing Electronics with Nano optics. Even though we have several communicating methods like Electronic communication, the main reason why we have to go for photonics is “Photons are light (mass less) and fast and electrons are heavy and slow and never the twain shall meet”. In this Photonics communication photons play the prominent role unlike in Electronics. The wave length of light is of a few hundred nano meters, where as our nano sized particles is of a few nano meters so that we can control the light using nano sized particles which is a very interesting thing in communication. In this communication method we directly pass the message signal through light with out converting into electrical or any other signals that is we are replacing the lazy electrons with more prominent photons. If we can implement nano technology in photonics communication we can transmit information with in a fraction of a second for that matter with in no time. By just using Pico joules of energy, we can switch parts in a few hundred Pico seconds of time. So this is both incredibly fast and also incredibly sparing in terms of energy usage. Nano technology is starting to take a close look at processing visual images to greatly improve the information they can provide us that is Active image processing.

Manipulating Light with Crystals:
As our technology still seeks to increase the speed at which information travels, the scale gets global and we find the information super highway. Although the information super highway has often been used as just another name for the internet, it also describes the vast network of optical and electrical cables now used to carry information. Nano technology is set to take the next step and improve the highway again. This over complicated, axed-out scene could use some simplifying. Crystals designed on the nano scale could replace electrical routers by directing the light itself instead of first converting it into electrical signals. The fiber-optic cables we use to carry information are potentially capable of transferring data at 10 to 40 Gbps. But most electrical routing occurs at less than 1% of that rate if we transfer to an all-optical router we could route most data packets in less than 1 trillionth of a second, pushing routing speed till it can handle the full capacity of the fiber-optic cable network. Before we can look at the details of how such an all-optical router would work, we need to look at the nano- scale pieces of light that our crystals will be dealing with. These pieces are called photons and the science of manipulating such pieces of light is known as photonics.

Getting hooked on Photonics:
A photon is the smallest unit of light and doesn't really have a shape or size and mass. They are the building blocks of light and they travel normally in big groups. The information super highway requires orderly photons for information transmission. So, orderly photons have to be made before they can be used as signal carriers. The trick is photons can't really carry anything (as they are weightless) so they are not the messenger, they are also the message. By varying the number of photons we ca form a code of high and low pulses. When we work at the nano scale, we rarely encounter large mobs of photons instead; we have to deal with a few photons at a time. If our nano-crystal accidentally stops just one of the photons, we have immediately lost most of our information. Stopping light is ridiculously easy. Photons love to be absorbed by just

about any thing. And those things that don’t absorb light usually reflect it. Thus the photon messenger must face getting either sucked up or bounced. Controlling where photons are absorbed and where they are deflected is the business of photonics and the concern of all nano-scale optical devices. Most of the time, we want those photons deflected as a means of moving information along a path, bouncing photons to their final destination. In order to do that we create and check the IDs for the photons.

Wavelengths: Creating nano-size IDs
The photons can be considered as a wave because they are vibrating and they can be considered as particle depending on the situation. Photons have detectable vibrations. In fact the length of the space it takes for them to go through one cycle of vibration determines the wavelength of a distinct bunch of photons. Moist of the light we dealt with as a wave length of few hundred nano meters. And it turns out that any nano-crystal router is going to have used the wave lengths of photons as a way to identify them. The nanoscopic crystal identifies different wavelengths of light by responding to how they travel. In fact different wavelengths of light travel at different angles when they are passing through a medium. Optical communication is a pretty exclusive night club. Usually we allow only 1500 nano meter wavelength into the party because it’s the telecommunications standard wave length. So if crystal-based router s specifically designed to the 1500 nano meter wave length, it can be integrated into the inter net. It's important to note that different materials and crystal designs can be specifically tailored for a specific wavelength and only this specific wavelength excluding all others. That is if the photons don’t have the 1500nm ID, they cannot come into our communication system.

Controlling light: Photonic band gaps
Photons and electrons don’t have a lot in common but similar technology is needed to manipulate each of them. When we replace a slow electrical device with a quicker optical one the same old design can be used to generate ideas for the new one. To get semi transparent structures, we have to add just enough of the right impurities to our nano crystals. These semi transparent structures can be used to filter the photons. Since different photons have different wave lengths, by varying the geometry of the nano

crystal, we can change which energies get stopped by the opaque part of the crystal and that pass through the transparent portion. To understand controlling of light much better, imagine a large bowl with the marbles spinning around inside. Here the marbles are our photons and the bowl is the crystal.

The fastest moving photons spin around near the top, the slowest photons spin near the bottom and most of the photons spin some where between. Now if we put some putty in a circle around the middle of the bowl, the marbles that want to spin around at that level either get stuck in the putty or bounce to higher or lower parts of the bowl-and the marbles already in the high or low sections cant cross the putty that is the putty functions as a band gap. It separates photons into groups that have different levels of energy as shown in the above figure. Now we introduce the concept of photonic band gaps. The photons that have a particular wave length have to travel with in the photonic band gap restricted from the surrounding material. We can create these band gaps in one of the two ways  By exploiting geometric abnormalities in the crystal  Using impurities in the crystal By exploiting the geometric abnormalities in the crystal, we can create distinct energy levels in the band gap so that some photons may travel through them. Some photonic crystals are grown the same computer chips are made. We can create a honey comb pattern in the crystal by etching opaque circles into each 2-D layer, spacing them at regular intervals. As we build up the layers with the circles always in same places, the circles become large. The places where the rods are absent are empty spaces. The chemical properties of these rods shape the photonic band gap. Light won’t travel through the rods. Now, by removing enough rods we can make nano-size spaces to allow the light.

We are insulating light of a specific wavelength to be guided through our nano crystal. The above figure shows a top view of a photonic crystal. When the light approaches the turn in the crystal, it bends to follow the path. The apparent bending and spreading of waves can be used to control the light.

Nano Lasers:
Along with routers, modern communication systems also need repeaters for the purpose of amplifying the fading light signals. To do that we have to construct Nano lasers. The photonic band gaps also called optical cavities play a crucial role in constructing Nano lasers. When light enters an optical cavity the photonic band gap keeps the light bounce back and forth in the cavity- gaining energy, tightening into a coherent beam. To get the laser effect a gain medium has to be placed in an optical cavity. When photons enter into such a medium they get amplified and they provide complete information. To make a Nano laser, a photonic crystal is used to create a cavity that's almost as small as the wave length of the photons. This cramped space forces the photons to travel in nearly parallel lines, until the intensity of the light reaches the theoretical limits. We have to provide a small electric current to burst out of the laser. Thus by using Nano laser we can amplify our information signals.

Optical Switching: Nano defects to the rescue!
Being able to form different paths for photons, we must be able switch between those parts. That is we have to “flip the switch” in order for a nano optical routing device to work. So we have to see the photonic band gaps in another way. We will look at the bowl of marbles once again. The putty that separates the top and bottom halves can be divided into number of different sub energy levels for our convenience. Next we make small holes in the putty layer that allow our photons to move freely between the two halves. All of this is brilliantly illustrated in the following figure.

Now, if there were two lines of putty spaced a bit apart from each other and holes in each of those lines, a photon can pass into the space created by the two lines of putty and then roll around until it came upon another hole, ending up once again in the other half of the bowl. These holes allow a few trespassers across the border. Photons never cross directly but they can go to the intermittent level and then tom the other side. So these levels are said to be the little wrinkles or folds that led photons cross over. Most of the time, these levels are hard-wired into the crystal such as additional photons. By regulating those photons, we can make an optical switch that can turn on and of by shining a light at it. So we are able to construct an optical switch.

Making the switch: Photons on a nano-highway
Researches at Cornell University have already developed some of the nano technology needed to create an all-optical switch. Now, we will go deep in the manufacturing of optical switch. The photonic equivalent is called a “ring –router” and is pictured as below. The ring router has intermittent levels in its photonic band gap and we can manipulate the levels by introducing the photons of the proper wavelengths. When the right beam of photons comes along, the router changes its task instead of allowing light to zip around in it and go through it, it absorbs the new wave length or passes it of in another direction. The following figure shows how such a switch might work.

Notice that there are two beams we have to keep track of The signal beam (the one that either gets blocked or passed through the router).  A switch beam (The one that turns the ring router on and off). So we have our nano routers which are extremely quick and they route nano size portions of light.

Magic with Mirrors
Mirrors are a handy, easy way to direct light around and they control the information super highway. Reflecting large portions of light beam is pretty easy. When we change the direction that mirror faces, we change the direction that the information flows. While it doesn’t get the details sorted out, it does move a lot more data around than the photonic crystals could by them selves. Combining these two techniques to provide a more well-rounded and versatile router. We will probably have to settle for one of the many other ways to move mirror-to beam-steer. The following figure shows a fairly tiny mechanical solution: 256 mirrors on a few square cm of Silicon.

Using electrical pulses to move the mirrors provides even final control and allows faster beam-steering.

Light steering: Nanotechnology at the wheel
Aiming a mirror at the nano scale requires precise control of tiny electro mechanical devices. Pushing or pulling on a mirror adjust the angle at which light bounces off, even small changes in angle can lead to big differences in the final destination of beam of light. To tightly regulate the angle of a mirror on the nano scale, we have to spread out super tiny electro mechanical devices around its space. So for the implementation of this Nanotechnology is essential. Researchers at Boston Micro machines are using electrostatic force to regulate the angle of mirrors.

Conclusion
No matter which type of mirror-position in device we would like to use, the final step is in including it with the nano-router is fairly simple i.e., we use the mirror to direct the information in the form of light thus speeding up our telecommunication. At the end, the nano-router’s use of mirrors will probably be limited to bulk transmission of data, photonic crystals are faster for smaller chunks of information.